Aluminum alloy



atented Aug. 1, 1933 1,920,262 ALUMINUM ALLOY Louis W. Kemp! and Walter A. Dean, Cleveland,

Ohio, assignors to Aluminum Company of America, Pittsburgh, Pa., a Corporation of Pennsylvania No Drawing. Application July 23, 1932 Serial No. 624,345

2 Claims. (Cl. 75-1.)

This invention relates to aluminum base alloys characterized, at elevated temperatures, by high physical properties. Such alloys are used, for instance, in the manufacture of pistons or 5 cylinder heads for internal combustion engines or in other adaptations where temperatures of use frequently considerably exceed room temperatures,

. Alloys of the general nature herein described have already been disclosed in the copending application of R. S. Archer and L. W. Kempf, Serial No. 403,353, filed October 29, 1929, and in the copending application of W. A. Dean, Serial No. 552,557, filed July 22, 1931. These copending applications relate to aluminum base alloys containing copper, silicon, and nickel, the copper not exceeding 8 per cent. In application Serial No. 403,353 aforementioned, there is disclosed an alloy exhibiting said high temperature properties and sumcient strength at room temperature to fully serve its purpose. In application Serial No. 552,557 aforementioned, there is disclosed an alloy which, by reason of a certain nickel content, has a high strength in the cast condition, a considerably refined crystalline structure, and an increased ductility, these properties being obtained without material impairment of the properties which, characterize the alloys disclosed inthe earlier application Serial so No. 403,353. a

We have discovered that it is possible, by a modification of the earlier known alloys of this type, to simultaneously preserve the advances made in the latest exemplifications of so-called high temperature alloys and at the same time efiect furtherimprovement in the properties of the alloy at elevated temperatures, namely, in the neighborhood of 400 Fahrenheit to 600 Fahrenheit. This we have accomplished by pro- 40 viding an aluminum base alloy having a nickel content of about 2 per cent to about 6 per cent by weight, a silicon content of about 5 per cent to about 12 per cent by weight, and a copper 9 content above 8 per cent, the copper content 5 usually being about 9 per cent to about 14 per cent by weight. The balance of the alloy may be aluminum in any of the grades which are available commercially. The alloy may likewise contain from about 0.01 per cent to about 1- per cent of a high melting point metal, such as titanium, molybdenum, tungsten, manganese, chromium, or iron. More than one of these high melting point metals may be used in combination, provided their total amount does not exceed about 1 per cent of the whole. In alloys of the above composition, we have secured very favorable physical properties at elevated temperatures, including higher hardness and tensile strength and, in addition, a relatively high impact resistance at all temperatures and better tensile properties at room temperatures.

In order to describe some of the advantages of our alloys, the following is a comparison between alloy A, which is the preferred alloy made in accordance with our invention, and alloys B and C, which represent alloys known prior to our invention and disclosed in the aforesaid copendlng Since experience has demonstrated that for properly evaluating two or more alloys with reference to their behavior at elevated temperatures, the alloys should be tested under substantially identical conditions, factors such as the length of time at temperatre before testing, initial thermal treatments, rate at which the load is applied in tensile testing, etc., were maintained as nearhr equal as possible in the tests about to be described.

Alloy A in the sand cast condition had a tensile strength at room temperature of 25,300 pounds per square inch. At a temperature of 400 Fahrenheit, the alloy had a tensile strength of 24,800 pounds per square inch, and at 600 Fahrenheit the alloy had a tensile strength of 18,000 pounds per square inch.

A sand casting made of alloy B had a tensile strength of 19,000 pounds per square inch at room temperature. At 400 Fahrenheit, its tensile strength was 17,000 pounds per square inch, and at 600 Fahrenheit its tensile strength was 12,700 pounds per square inch.

Alloy C, sand cast, had a tensile strength at room temperature of 27,000 pounds per square inch. At 400 Fahrenheit, the tensile strength of alloy C was about 24,000 pounds per square inch. and at 600 Fahrenheit the tensile strength oil alloy C was about 15,500 pounds per square inch.

Upon comparison of the properties of A, and C, it will be noted that alloy A lost on?! Bil about 500 pounds per square inch in tensile strength when the temperature was raised from room temperature to 400 Fahrenheit, while alloy B, under the same conditions, lost 2,000 pounds per square inch in tensile strength. As the temperature was raised to 600 Fahrenheit, it will be noted that the tensile strength of alloy A was only 1,000 pounds per square inch less than the tensile strength of alloy B at room temperature, and that the tensile strength of alloy A at 600 Fahrenheit exceeded the tensile strength of alloy C by about 2,500 pounds per square inch, alloy C having lost in tensile strength about 12,000 pounds per square inch while alloy A lost only about 7,000 pounds per square inch.

Another interesting comparison which illustrates the advantageous properties of the alloys which are the subject ofthis invention are the comparative impact resistance values in a standard impact testing machine both at room temperature and at 600 Fahrenheit. At room temperature alloy A has an impact resistance of 64.5 foot pounds per square inch and alloy B has an impact resistance of 47.5 foot pounds per square inch. At 600 Fahrenheit alloy A has an impact resistance of 66.5 toot pounds per square inch and alloy B has an impact resistance of 46.0 feet pounds per square inch.

The alloys which are the subject of the present invention may be heat-treated forthe purpose of improving their tensile and hardness properties or they may be otherwise thermally treated for the purpose of removing strains or stabilizing volume changes. For such purposes, the heattreatment and other thermal processes well known to those skilled in the art may be used.

What we claim is:

1. An alloy consisting of about 12 per cent by weight of copper, about 7 per cent by weight oi silicon, and about 4 per cent by weight of nickel,

. the balance being substantially aluminum.

2. An alloy consisting of from 9 to about i i per cent by weight of copper, from about 5 to about 12 per cent by weight of silicon, and from about 2 to about 6 per cent by weight of nickel,

the balance being substantially aluminum, said alloy being characterized by an internal structure relatively highly resistant to deterioration of properties under the influence of elevated temp ratures.

LOUIS W. WALTER A. DEAN. 

